The present invention is a liquid silicone rubber composition. More specifically, the present invention is a liquid silicone rubber composition which has superior weather resistance and mechanical characteristics, as well as good high-voltage electrical insulating characteristics such as tracking resistance, are resistance, and erosion resistance. Examples of possible uses of this composition include anode caps, plug boots, insulators, and flame-retardant electrical wiring.
In the past the mixing of large quantities of inorganic fillers such as powdered aluminum hydroxide, powdered aluminum oxide, or powdered quartz with silicone rubber compositions used in applications requiring high-voltage electrical insulating characteristics, such as anode caps, plug boots, insulators, and flame-retardant electrical wiring has been proposed. For example, in Japanese Patent Application Kokoku No. 53-35982 and U.S. Pat. No. 3,965,056 it is indicated that a silicone rubber composition in which the ordinary electrical insulating characteristics are improved can be obtained by heating a mixture of a polyorganosiloxane which forms a rubber elastic material when cured by heating and an aluminum hydrate for 30 minutes or longer at a temperature exceeding 100.degree. C. Furthermore, it is indicated in Japanese Patent Application Kokai No. 4-209655 that a mixture consisting of a polyorganosiloxane composition which forms an elastomeric material when heat-cured using an organic peroxide, (b) aluminum hydroxide and (c) an organosilane or organosiloxane which has phenyl groups will form a silicone rubber composition with superior high-voltage electrical insulating characteristics. In addition, a silicone rubber composition for use in the covering of electrical wires which consists of a polyorganosiloxane and an inorganic zinc compound is proposed in Japanese Patent Application Kokoku No. 62-26124.
However, in all of these conventional examples the high-voltage electrical insulating characteristics of the silicone rubber materials are still not totally adequate. Furthermore, under conditions of harsh contamination or exposure to the elements deterioration phenomena such as tracking and erosion occur due to high electrical stress so that the high-voltage electrical insulating characteristics show a conspicuous deterioration. Furthermore, silicone rubber compositions obtained by a high degree of filling with the abovementioned inorganic fillers have an extremely high viscosity and are therefore difficult to use in applications requiring fluidity, such as injection-molded materials. Moreover, such compositions also have a low mechanical strength.
Accordingly, a liquid silicone rubber composition which has an appropriate degree of fluidity prior to curing, which is superior in terms of moldability, and which forms silicone rubber molded articles that have good high-voltage electrical insulating characteristics and high mechanical strength following molding is desired.
Specifically, the object of the present invention is to provide a liquid silicone rubber composition which has an appropriate degree of fluidity prior to curing, which is superior in terms of moldability, and which forms silicone rubber molded articles that have high mechanical strength and good high-voltage electrical insulating characteristics following molding.